Water heater with insulating layer

ABSTRACT

A water heater includes: an inner tank having an internal cavity configured to hold water therein; a heating device residing in the internal cavity; an outer lining that surrounds the inner tank, a gap being present between the outer lining and the inner tank; and insulation material located in the gap. The gap is under a vacuum of between about 5 and 200 microns. In this configuration, the water heater can have an R value in excess of 500. With this level of insulative capacity, water stored in the water heater may lose only 2° F. or less over a 24 hour period, thereby substantially outperforming conventional water heaters.

RELATED APPLICATION

This application claims priority from U.S. Provisional PatentApplication No. 61/346,582, filed May 20, 2010, the disclosure of whichis hereby incorporated herein in its entirety.

FIELD OF THE INVENTION

The present invention is directed generally to heating devices, and moreparticularly to water heaters.

BACKGROUND OF THE INVENTION

Typical water heaters that are currently available utilize foam orfiberglass insulation around a tank that heats and stores hot water.Electricity, gas, geothermal or solar energy ordinarily provides theheat source for the water. The insulation medium that surrounds the tanktypically has an R value (a well-known measure of thermal resistance) of7 to 12. These values typically result in a heat loss of 2° F. or moreper hour. As a result, as a general rule water heaters need tofrequently fire and reheat the stored water to be able to provide waterof the desired temperature upon demand. Water heater life is usually7-13 years—with proper maintenance—and most units typically last lessthan 10. Heat pump and gas condensing units associated with conventionalwater heaters also generally require additional maintenance and partsreplacement.

Heating water is typically the second largest energy requirement in thehome. As such, manufacturers are continually seeking ways to reduceenergy input. Many efforts have focused on reducing the electric/gasinput requirements. Some manufacturers are pursuing heat pump and gascondensing product innovations to reduce energy needs; however, theseapproaches can be expensive and are somewhat unproven.

Tank-less water heaters are another alternative. However, tankless waterheaters available today tend to be limited in water flow capacity duringdemand and usually require significant service over time. Units aresized based on the number of “hot outlets” that are needed for a givennumber of residents of a household. Units for many outlets/people tendto be expensive and, even with the energy tax credits that are currentlyavailable, recovering the cost of the unit based on energy savings israre.

SUMMARY OF THE INVENTION

As a first aspect, embodiments of the present invention are directed toa water heater. The water heater comprises: an inner tank having aninternal cavity configured to hold water therein; a heating deviceresiding in the internal cavity; an outer lining that surrounds theinner tank, a gap being present between the outer lining and the innertank; and insulation material located in the gap. The gap is under avacuum of between about 5 and 200 microns. In this configuration, thewater heater can have an R value in excess of 500. With this level ofinsulative capacity, water stored in the water heater may lose only 2°F. or less over a 24 hour period, thereby substantially outperformingconventional water heaters.

As a second aspect, embodiments of the present invention are directed toa water heating system, comprising: a heat exchange fluid (HEF) tank;one or more solar panels; a first line fluidly connecting the HEF tankwith the solar panels; a water heater, the water heater including a heatexchanger; a second line fluidly connecting the HEF tank with the heatexchanger; a third line fluidly connecting the solar panels with theheat exchanger; and a pump located on one of the first, second or thirdlines.

As a third aspect, embodiments of the present invention are directed toa water heating system, comprising: a heat exchange fluid (HEF) tank;one or more solar panels; a first line fluidly connecting the HEF tankwith the solar panels; a water heater, the water heater including a heatexchanger; a second line fluidly connecting the HEF tank with the heatexchanger, wherein one of the first line and the second line includes afirst valve, and wherein the second line includes a second valve; athird line fluidly connecting the solar panels with the heat exchanger,the third line including a third valve; a pump located on one of thefirst, second or third lines; and a controller operably associated withthe first, second and third valves.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a longitudinal section view of a water heater according toembodiments of the present invention.

FIG. 2 is a longitudinal section view of the outer lining of the waterheater of FIG. 1 prior to its assembly with the inner tank.

FIG. 3 is a longitudinal section view of the inner tank of the waterheater of FIG. 1.

FIG. 4 is a longitudinal section view of the inner tank of FIG. 3 withan outer cap attached thereto.

FIG. 5 is a longitudinal section view of the water heater of FIG. 1 withthe inner tank and outer cap of FIG. 4 assembled with the outer liningof FIG. 2.

FIG. 6 is a side view of the water heater of FIG. 1 in an assembledcondition.

FIG. 7 is a schematic diagram of an exemplary residential solar heatingsystem employing a water heater of FIG. 1 according to embodiments ofthe present invention.

FIG. 8 is a schematic diagram of an exemplary commercial solar heatingsystem employing water heaters according to embodiments of the presentinvention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention will now be described more fully hereinafter, inwhich preferred embodiments of the invention are shown. This inventionmay, however, be embodied in different forms and should not be construedas limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. In the drawings, like numbers refer to like elementsthroughout. Thicknesses and dimensions of some components may beexaggerated for clarity.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. As used herein the expression“and/or” includes any and all combinations of one or more of theassociated listed items.

In addition, spatially relative terms, such as “under”, “below”,“lower”, “over”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of the device in use or operation in addition tothe orientation depicted in the figures. For example, if the device inthe figures is turned over, elements described as “under” or “beneath”other elements or features would then be oriented “over” the otherelements or features. Thus, the exemplary term “under” can encompassboth an orientation of over and under. The device may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein interpreted accordingly.

Well-known functions or constructions may not be described in detail forbrevity and/or clarity.

Referring now to the drawings, a water heater according to embodimentsof the present invention, designated broadly at 10, is shown in FIG. 1.The water heater 10 includes an inner tank 12 in which water is stored.The inner tank 12 may be formed of a number of different materials; inthis embodiment, the inner tank 12 is formed of stainless steel,preferably type 300 stainless steel, or glass-lined carbon steel

A heat exchanger 14 is located within the inner tank 12 that providesenergy to heat water stored within the inner tank 12. The heat exchanger14 can be of any design or configuration known to those of skill in thisart to be suitable for transferring heat to a fluid medium. The waterheater 10 also includes a cold water inlet 16 and a hot water exit 18through which water can flow into and out of the inner tank 12. In thisembodiment, a pressure and temperature relief valve and pressure gauge20 is mounted on the hot water exit 18. A sacrificial anode 22 alsoextends into the inner tank 12. These components may be of conventionaldesign known to those of skill in this art and need not be described indetail herein.

The water heater 10 also includes an outer lining 24 (see also FIG. 2).The outer lining 24 comprises an outer layer 26 (in this embodimentformed of a thermoplastic such as an extruded polypropylene copolymer ora metal such as stainless or carbon steel) and an inner layer 28 thatserves to provide a vacuum-tight environment within the outer lining 24.In some embodiments, the inner layer 28 is formed of thin aluminum; inother embodiments, the inner layer 28 is formed of a thin layer ofceramic microspheres and/or fiberglass wrap.

As can be seen in FIG. 1, the outer lining 24 is formed to be largerthan the inner tank 12, such that a gap 30 exists between the inner tank12 and the outer lining 24. The gap 30, which is typically between 3 and4 inches in thickness, is filled with a highly insulative material 32.Exemplary highly insulative materials include ceramic microspheres(e.g., glass microspheres available from 3M, Inc., Minneapolis, Minn.),perlite, and a two-piece warp formed of foil and tissue (available underthe name “Superinsulation”). Also, in the illustrated embodiment, thegap 30 is subjected to a vacuum of between about 5 and 200 microns, andin other embodiments to a vacuum of between about 5 and 20 microns. Avacuum pump port 25 with a vacuum valve 29 extends into the gap 30 andis configured to be connected to a vacuum pump (not shown). Someembodiments may have no vacuum within the gap 30. As illustrated, thewater heater 10 may include supports 27 between the inner layer 28 andthe inner tank 12 to maintain the spacing of the gap 30.

In this configuration, the water heater 10 can have an R value in excessof 500. With this level of insulative capacity, water stored in thewater heater 10 may lose only 2° F. or less over a 24 hour period,thereby substantially outperforming conventional water heaters. Becausethe temperature of the stored water is so much more stable than that ofconventional water heaters, much less energy is required to maintain thetemperature of the water. Also, the absence of moving parts in the waterheater 10 can increase its life span, which may be up to 30 years ormore.

The energy to operate the heat exchanger 14 to heat the water stored inthe inner tank 12 may be provided in any form known to be suitable tothose of skill in this art. For example, the energy may be electrical,gas, solar, wind, geothermal, or the like. Solar, wind and geothermalenergy may be particularly appealing in some embodiments due to theinexpensive nature of generating the energy. As such, it is contemplatedthat the heat exchanger 14 may be connected with one or more solarpanels or cells, a wind-driven turbine, or a geothermal cell.

Referring now to FIGS. 2-6, a manufacturing and assembly methodaccording to embodiments of the present invention is illustrated. Thewater heater 10 shown therein has an injection-molded thermoplasticouter layer 26 and a ceramic microsphere inner layer 28 that comprisethe outer lining 24. FIG. 2 shows the outer lining 24 after it has beeninjection molded; in this embodiment, the ceramic microspheres of theinner layer 28 are bonded to the outer layer 26 during the injectionmolding process. Typically, the outer layer 26 is between about 0.25 and0.375 inches in thickness, and the inner layer 28 is between about 0.25and 0.375 inches in thickness. In this embodiment, the outer layer 26includes annular ribs 26 a to improve the strength of the outer layer 26under vacuum. Also, in this embodiment the outer lining 24 is split intothe large, open-ended portion shown in FIG. 2 and a cap that fits overthe open end. In other embodiments, the outer layer 28 may comprise athin metallic foil.

Referring now to FIG. 3, an exemplary configuration of an inner tank 12′is shown. The inner tank 12′ is similar to the inner tank 12 describedabove, but includes electrically-energized heating elements 14′ ratherthan the heat exchanger 14. FIG. 4 shows the attachment of the plasticcap (lined with ceramic microspheres) to the upper end of the inner tank12. Also, a steel ring 40 is attached to the middle of the inner tank12; the ring includes support rods 42 that brace the inner tank 12 whenit is inserted into the outer lining 24. FIG. 5 shows the inner tank 12lowered into the outer lining 24 and the cap of the outer lining 24sealed to the remainder of the outer lining 24. FIG. 6 is a front viewof the completed water heater 10.

It will also be understood to those of skill in this art that the heatexchanger 14 may be replaced with another variety of heating device,such as an electrically driven heating element or the like.

Referring now to FIG. 7, an exemplary solar heating system, designatedbroadly at 100, is illustrated therein. As can be seen in FIG. 7, thesystem 100 includes a water heater 10 of the variety described above.The system 100 also includes solar panels 102 of conventionalconstruction that receive solar energy and convert it to heat. Those ofskill in this art will understand the construction and operation of thesolar panels 102, which need not be discussed in detail herein. Thesystem 100 further includes a heat exchange fluid (HEF) tank 152 thathouses a heat exchange fluid (e.g., a mixture of ethylene glycol andwater). The interconnections between the solar panels 102, the waterheater 10 and the HEF tank 152 are discussed below.

A line 104 connects the solar panel 102 with the exit port of the heatexchanger 14 located in the water heater 10. A solenoid valve 106 islocated on the line 104, as is a check valve 108.

A line 110 extends between the entry port of the heat exchanger 14 andan exit port of the glycol tank 152. A solenoid valve 118 is located onthe line 110, as is a pump 150. A second solenoid valve 136 is locatedon the line 110 near the HEF tank 152.

A line 111 extends between the solar panels 102 and an entry port of theHEF tank 152. A check valve 138 is located on the line 111 near the HEFtank 152, and a check valve 130 is located on the line 111 near thesolar panels 102.

A branch line 140 extends between the lines 102, 111 to create a fluidcircuit with the solar panels 102 that includes the check valve 130 andthe solenoid valve 106. A solenoid valve 140 is located on the branchline 140.

A branch line 132 extends between the lines 110, 111 to create a bypassof the HEF tank 152. A solenoid valve 128 is located on the branch line132. In some embodiments, this line is omitted.

A branch line 114 extends between the lines 102, 110 to create a bypassof the water heater 10. A solenoid valve 116 is located on the branchline 114.

An HEF cooling line 120 forms a loop with the line 110, meeting the line110 on either side of the solenoid valve 118. The HEF cooling line 120includes a solenoid valve 124 and a check valve 122.

The system 100 also includes three thermocouples 144, 146, 148. Thethermocouple 144 is located on the water heater 10 and detects thetemperature of the water inside. The thermocouple 146 is located on theHEF tank 152 and monitors the temperature of the heat exchange fluidinside. The thermocouple 148 is located on the line 111 and monitors thetemperature of the heat exchange fluid therein.

The system 100 also includes a controller 154. The controller 154 isconfigured for communication with the solenoid valves 106, 112, 116,118, 124, 128, 136, 142 and with the thermocouples 144, 146, 148.

In operation, the system 100 begins with the solenoid valves 136, 118,112 and 106 open and the solenoid valves 128, 124, 116 and 142 closed.This arrangement creates a fluid circuit in which a glycol/water mixtureis conveyed by the pump 150 from the solar panels 102 to the HEF tank152, then to the heat exchanger 14 of the water heater 10, and back tothe solar panels 102. The heat exchange fluid can be heated in the solarpanels 102 and transported to the HEF tank 152. Heated heat exchangefluid is transported to the heat exchanger 14, where it heats water inthe water heater 10. The heat exchange fluid then returns to the solarpanels 102 for further heating.

If the thermocouple 144 associated with the water heater 10 detects thatthe temperature of the water therein is above a threshold temperature(e.g., 125° F.), the controller 154 signals the solenoid valve 112 toclose and the solenoid valve 116 to open. This forms a circuit in whichthe water heater 10 is bypassed, as the water temperature is alreadyadequate for use.

If the thermocouple 146 associated with the HEF tank 152 detects thatthe temperature of the HEF tank 152 exceeds a threshold temperature(e.g., 175° F.), the controller 154 signals the solenoid valve 136 toclose and the solenoid valve 128 to open. This action removes the HEFtank 152 from the circuit described above and results in the cooling ofthe heat exchange fluid. If temperature measured by the thermocouple 146drops below a threshold temperature (e.g., 170° F.) and the temperaturemeasured by the thermocouple 148 is above that threshold temperature,the solenoid valve 136 opens and the solenoid valve 128 closes torestore the circuit described above in order to introduce additionalheat energy into the HEF tank 152.

If the thermocouple 148 (which measures the temperature of the heatexchange fluid shortly after it exits the solar panels 102) detects atemperature above a threshold temperature (e.g., 175°), and if thetemperature at the thermocouple 146 is above its threshold and thetemperature at the thermocouple 144 is above its threshold, thecontroller 154 signals the solenoid valves 112, 142, 118, 136 to closeand solenoid valves 106, 124, 116, 128 to open. This action creates acircuit that lacks the HEF tank 152 and the water heater 12 and includesthe glycol cooling line 120. The pump 150 pumps the heat exchange fluidthrough the HEF cooling line 120 until the thermocouple 148 measures atemperature below its threshold temperature.

In the event that the thermocouples 144, 146 are above their thresholdtemperatures and the thermocouple 148 is below its thresholdtemperature, the controller 154 signals the pump 150 to cease operation.

In the event that the thermocouple 148 falls below a low thresholdtemperature (e.g., 120°), the controller 154 signals the solenoid valve106 to close and solenoid valve 142 to open. The solenoid valve 128 alsocloses and the solenoid valve 136 opens. This action creates a circuitthat lacks the solar panels 102 and utilizes heat exchange fluid fromthe HEF tank 152. This circuit may be used when the solar panels 102 aregenerating insufficient energy to heat the heat exchange fluid (e.g., atnight or during a cloudy day). This capacity can assist the system inoperating adequately in low solar energy inputs periods by utilizingheat energy that is stored in the heat exchange fluid within the HEFtank 152. Those skilled in this art will note that other materials, suchas molten salt (sodium acetate trihydrate), may be employed as the heatexchange fluid.

Referring now to FIG. 8, a commercial water heating system, designatedat 300, is illustrated therein. The system 300 includes three waterheaters 10 a, 10 b, 10 c that are similar to the water heater 10described above. The system 300 includes solar panels 302 of the typedescribed above. The remainder of the system 300 is described below.

A heat exchange fluid line 304 extends between the solar panels 302 andthe tanks 10 a, 10 b, 10 c. A pump 352 is located within the line 304. Acheck valve 305 is located between the solar panels 302 and the pump352. Branch lines 306, 308, 310 extend from the line 304 to the entryports of the heat exchangers 14 within, respectively, the tanks 10 a, 10b, 10 c. Each of the branch lines 306, 308, 310 includes a respectivesolenoid valve 312, 314, 316.

A second heat exchange fluid line 318 extends between the tanks 10 a, 10b, 10 c and the solar panels 302. Three branch lines 320, 322, 324extend between the line 318 and the exit ports of the heat exchangers 14of, respectively, the tanks 10 a, 10 b, 10 c. A respective check valve326, 328, 330 is located on each branch line 320, 322, 324. A solenoidvalve 331 is located on the line 318 between its intersection with thebranch line 324 and the solar panels 302.

A cold water supply line 346 leads from a cold water source 347 to thetanks 10 a, 10 b, 10 c. Branch lines 348, 350, 354 lead from the line346 to, respectively, the tanks 10 a, 10 b, 10 c. A respective checkvalve 356, 358, 360 is located on each branch line 348, 350, 354.

A hot water line 332 leads from the tanks 10 a, 10 b, 10 c to a hotwater destination 333. Branch lines 334, 336, 338 extend between theline 332 and respective tanks 10 a, 10 b, 10 c. A respective solenoidvalve 340, 342, 344 is located on each branch line 334, 336, 338. Amixing valve 362 connects the cold water supply line 346 with the hotwater supply line 332.

A respective thermocouple 364, 366, 368 is mounted on each tank 10 a, 10b, 10 c to measure the water temperature therein. A thermocouple 370 islocated on the line 304 between the check valve 305 and the pump 352.

The system 300 includes a controller 380 that is configured to controlthe operation of the solenoid valves 312, 314, 316, 331, 340, 342, 344and the thermocouples 364, 366, 368, 370.

In operation, the system 300 begins with the tanks 10 a, 10 b, 10 cbeing filled with cold water, and all of the solenoid valves 312, 314,316, 331, 340, 342, 344 being closed. When the system 300 is activated,solenoid valve 331 is opened, as is the solenoid valve 312. This actioncreates a circuit for the heat exchange fluid between the solar panels302 and the tank 10 a, wherein the heat exchange fluid is heated via thesolar panels 302 and pumped through the circuit by the pump 352. Whenthe thermocouple 364 senses that the water in the tank 10 a has reacheda certain temperature (e.g., 160° F.), the controller 380 closes thesolenoid valve 306 and opens the solenoid valve 308. This action createsa circuit between the solar panels 302 and the tank 10 b. When the waterin the tank 10 b reaches the desired temperature as measured by thethermocouple 366, the controller 380 closes the solenoid valve 308 andopens the solenoid valve 310, thereby creating a circuit between thesolar panels 302 and the tank 10 c. The tank 10 c is then allowed toreach the desired temperature.

If the temperature measured by thermocouple 370 differs by no more thana predetermined magnitude (e.g., 15° F.) from the temperature measuredby the thermocouples 364, 366, 368, the controller 380 signals the pump352 to cease operation.

If the event water is needed at its destination 333, the solenoid valve340 opens, and water is supplied to the mixing valve 362 from the tank10 a. If the thermocouple 364 senses that the water temperature in thetank 10 a is below a predetermined threshold (e.g., 100° F.), thesolenoid valve 340 closes and the solenoid valve 342 opens and supplieswater to the mixing valve 362. If the thermocouple 366 senses that thewater temperature in the tank 10 b is below a predetermined threshold,the solenoid valve 342 closes and the solenoid valve 344 opens andsupplies water to the mixing valve 362. If the thermocouple 368 sensesthat the water temperature in the tank 10 c is below a predeterminedthreshold, the solenoid valve 344 closes. Once demand for water is met,water in the tanks 10 a, 10 b, 10 c is heated sequentially in the mannerdescribed above.

The foregoing embodiments are illustrative of the present invention, andare not to be construed as limiting thereof. Although exemplaryembodiments of this invention have been described, those skilled in theart will readily appreciate that many modifications are possible in theexemplary embodiments without materially departing from the novelteachings and advantages of this invention. Accordingly, all suchmodifications are intended to be included within the scope of thisinvention as defined in the claims. The invention is defined by thefollowing claims, with equivalents of the claims to be included therein.

1. A water heater, comprising: an inner tank having an internal cavityconfigured to hold water therein; a heating device residing in theinternal cavity; an outer lining that surrounds the inner tank, a gapbeing present between the outer lining and the inner tank; andinsulation material located in the gap; wherein the gap is under avacuum of between about 5 and 200 microns.
 2. The water heater definedin claim 1, wherein the insulation material comprises ceramicmicrospheres.
 3. The water heater defined in claim 1, wherein the outerlining comprises an inner layer and an outer layer.
 4. The water heaterdefined in claim 3, wherein the inner layer comprises one of a thinmetallic foil and a thin layer of ceramic microspheres.
 5. The waterheater defined in claim 3, wherein outer layer comprises one of athermoplastic or a metal.
 6. The water heater defined in claim 3,wherein the outer layer comprises a thermoplastic and the inner layercomprises a thin layer of microspheres.
 7. The water heater defined inclaim 6, wherein the outer layer is injection-molded and the inner layeris bonded to the outer layer during injection molding.
 8. The waterheater defined in claim 1, further comprising supports in the gap tomaintain the gap.
 9. The water heater defined in claim 1, wherein theouter lining has a two-piece construction.
 10. A water heating system,comprising: a heat exchange fluid (HEF) tank; one or more solar panels;a first line fluidly connecting the HEF tank with the solar panels; awater heater, the water heater including a heat exchanger; a second linefluidly connecting the HEF tank with the heat exchanger; a third linefluidly connecting the solar panels with the heat exchanger; and a pumplocated on one of the first, second or third lines.
 11. The waterheating system defined in claim 10, wherein the water heater comprises:an inner tank having an internal cavity configured to hold watertherein; a heating device residing in the internal cavity; an outerlining that surrounds the inner tank, a gap being present between theouter lining and the inner tank; and insulation material located in thegap; wherein the gap is under a vacuum of between about 5 and 200microns.
 12. The water heating system defined in claim 10, furthercomprising a fourth line fluidly connecting the first and second linesto isolate the HEF tank from the solar panels, the pump and the heatexchanger.
 13. The water heating system defined in claim 10, furthercomprising a fifth line fluidly connecting the first and third lines toisolate the solar panels from the HEF tank, the pump and the heatexchanger.
 14. The water heating system defined in claim 10, furthercomprising a sixth line fluidly connected to the second line and thethird line to isolate the heat exchanger from the solar panels, the pumpand the HEF tank.
 15. The water heating system defined in claim 10,further comprising a seventh line fluidly connected to two points on thesecond line, the seventh line providing a cooling loop for fluid in thesecond line.
 16. A water heating system, comprising: a heat exchangefluid (HEF) tank; one or more solar panels; a first line fluidlyconnecting the HEF tank with the solar panels; a water heater, the waterheater including a heat exchanger; a second line fluidly connecting theHEF tank with the heat exchanger, wherein one of the first line and thesecond line includes a first valve, and wherein the second line includesa second valve; a third line fluidly connecting the solar panels withthe heat exchanger, the third line including a third valve; a pumplocated on one of the first, second or third lines; and a controlleroperably associated with the first, second and third valves.
 17. Thewater heating system defined in claim 16, further comprising a fourthline fluidly connecting the first and second lines to isolate the HEFtank from the solar panels, the pump and the heat exchanger, the fourthline including a fourth valve operably associated with the controller.18. The water heating system defined in claim 17, further comprising afirst thermocouple associated with the HEF tank, and wherein thecontroller is configured to close the first valve and open the fourthvalve if the first thermocouple detects a temperature above apredetermined threshold.
 19. The water heating system defined in claim16, further comprising a fifth line fluidly connecting the first andthird lines to isolate the solar panels from the HEF tank, the pump andthe heat exchanger, the fifth line including a fifth valve operablyassociated with the controller.
 20. The water heating system defined inclaim 19, further comprising a second thermocouple associated with thefirst line, and wherein the controller is configured to close the thirdvalve and open the fifth valve if the second thermocouple detects atemperature below a predetermined threshold.
 21. The water heatingsystem defined in claim 16, further comprising a sixth line fluidlyconnected to the second line and the third line to isolate the heatexchanger from the solar panels, the pump and the HEF tank, the sixthline including a sixth valve operably associated with the controller.22. The water heating system defined in claim 21, further comprising athird thermocouple associated with the water heater, and wherein thecontroller is configured to close the second valve and open the sixthvalve if the third thermocouple detects a temperature above apredetermined threshold.
 23. The water heating system defined in claim16, further comprising a seventh line fluidly connected to two points onthe second line, the seventh line including a seventh valve operablyassociated with the controller and providing a cooling loop for fluid inthe second line.